Validation of the bioavailability of the second generation AjiProŽ-L using the in vivo plasma lysine response method
Six lactating multiparous Holstein (DIM = 64 to 314) equipped with ruminal cannulas were used in a 6 × 6 Latin square study with 7-d periods. The treatments were: 1) 0 g/d Lys, 2) 60 g/d of infused Lys, 3) 30 g/d of fed Lys from AjiPro®-L, 4) 60 g/d fed Lys from AjiPro®-L , 5) 30 g/d fed Lys from AjiPro®-L 2G, and 6) 60 g/d fed Lys from AjiPro®-L 2G. The infusion treatments consisted of Lys-HCl and were infused continuously into the abomasum via the ruminal cannulas. To ensure complete consumption, the AjiPro®-L and AjiPro®-L 2G were mixed with 1 kg of TMR and placed in tubs in front of the cows 30 min before each of the 3 daily feedings. Blood samples were obtained from each cow on the last 3 d of each period every 2 h, 4 times daily, from the tail vein, centrifuged, deproteinized, and composited into 1 daily sample/cow. Deproteinized plasma was analyzed for AA. Data for plasma AA concentrations (μmol basis) were analyzed using the PROC MIXED and PROC REG procedures of SAS. The bioavailability of AjiPro®-L, calculated by comparing the slopes of the infused and fed AjiPro®-L (Lys as % of total AA), was lower than previous evaluations using the same methodology. The infusion slope observed herein, obtained from 2 doses (0 and 60 g/d), was larger than those obtained previously, which were obtained using 3 doses (0, 30, and 60 g/d); this may explain the discrepancies among studies. In order to increase precision, it is recommended that at least 1 additional dose of infused Lys between 0 and 60 g/d should be used. It is important to note that the slope for the AjiPro®-L 2G (i.e., 0.01011; P < 0.01) was greater than the slope for the AjiPro®-L (i.e., 0.00682; P < 0.01) resulting in a 48% improvement in bioavailability of Lys from the AjiPro®-L 2G based on the ratio of the 2 slopes. It can be concluded that the bioavailability of Lys from AjiPro-L 2G was better than that from AjiPro-L. Further research is needed to test these 2 RP-Lys products.
AjiPro-L, Bioavailability, Lysine